The present invention relates to agricultural work vehicles having hitches by which implements are attached to the vehicles. More particularly, the present invention relates to agricultural work vehicles having electronic draft control systems that allow for the automatic controlling of the positioning of the hitches and attached implements.
Agricultural work vehicles such as tractors commonly tow implements such as plows that are attached to the vehicles by way of hitches. Often the positioning of an implement is controlled relative to the agricultural work vehicle to which the implement is attached by an electronic draft control (EDC) system of the agricultural work vehicle. Depending upon the type of agricultural work vehicle and/or implement being employed, an EDC system can control the positioning of an implement in a variety of ways.
For example, in the case where the agricultural work vehicle is a tractor, a tillage implement or plow can be attached to the tractor by way of a three-point hitch mounted at the rear of the tractor. A single quadrant lever, located in the tractor cab, is manually moved by the operator to generate position/draft commands which cause raising or lowering of the hitch. An EDC system including a microprocessor receives the position/draft commands and also receives feedback signals from draft sensors, which sense the draft on the hitch, and a position sensor, which senses the position of the hitch. The microprocessor responds to the position/draft commands and the feedback signals from the sensors by generating output signals for adjusting the position of the hitch. By varying the position of the hitch, the EDC system can vary the depth of the plow with respect to the ground, to account for varying resistance of the soil through which the plow is traveling.
Although such an implementation of an EDC system works well to control the positioning of the hitch and implement, the EDC system has an undesirable characteristic in that upward and downward pitching of the front portion of the tractor can occur when the EDC system attempts to produce changes in the positioning of the hitch and implement. The rear wheels of the tractor can act as a fulcrum of a lever formed by the body of the tractor. As a result, when the tractor is dynamically moving and towing the implement, or when the tractor is stationary but is raising or otherwise adjusting the positioning of the implement, variation in the amount of force between the implement and the rear of the tractor (applied by way of the hitch) can cause the front of the tractor to experience a corresponding change in downward or upward force. Further, particularly because of the tractor""s pneumatic tires, the tractor acts as a spring-mass system. As a result, changes in force experienced by the tractor can result in an undesirable pitching and vibration of the tractor.
It would therefore be desirable if a system was developed for implementation on an agricultural work vehicle that counteracted the pitching and vibration of the agricultural work vehicle occurring as a result of the operation of an EDC system on the agricultural work vehicle. It further would be desirable if such a system could be implemented easily and without great expense.
The present inventors have discovered that it is possible to counteract the pitching and vibration of an agricultural work vehicle due to the operation of an EDC system by controlling elements of a suspension system of the agricultural work vehicle. In particular, the present inventors have discovered that it is possible to counteract the pitching and vibration of the vehicle by controlling in a proportional manner, based upon output signals from EDC system itself, damping valves that govern the flow of hydraulic fluid to and from one or more suspension cylinders of the agricultural work vehicle.
In particular, the present invention relates to an apparatus for controlling variation in the pitch of an agricultural vehicle. The apparatus includes a controller that controls a position of an implement attached to the agricultural vehicle, and a first valve that is coupled to, and receives a first control signal from, the controller. The apparatus further includes a suspension cylinder having a first chamber that is hydraulically coupled to the first valve. The first control signal provided from the controller is functionally related to a first additional control signal provided by the controller, and the first additional control signal is used to determine the position of the implement.
The present invention further relates to an apparatus for controlling variation in the pitch of a vehicle. The apparatus includes a control means for controlling a position of a device coupled to a rear of the vehicle, a first suspension device for controlling the suspension of a front of the vehicle, and a first damping device for controlling a damping of the first suspension device. The first damping device is coupled to the first suspension device and to the control means. The first damping device controls the damping based upon a first control signal that is proportionally related to an additional control signal provided by the control means for controlling the position of the device.
The present invention additionally relates to a method of controlling variation in the pitch of an agricultural vehicle. The method includes providing a controller capable of controlling the positioning of an implement attached to the agricultural vehicle, and providing a suspension system on the agricultural vehicle that includes a first suspension device and a first damping device. The method additionally includes generating a first position control signal to produce a change in the positioning of the implement, and generating a first suspension control signal to produce a change in operation of the first damping device. The first suspension control signal is functionally related to the first position control signal.